This adds a context.Context parameter to NewFs and related calls.
This is necessary as part of reading config from the context -
backends need to be able to read the global config.
- add a directory to the optional Purge interface
- fix up all the backends
- add an additional integration test to test for the feature
- use the new feature in operations.Purge
Many of the backends had been prepared in advance for this so the
change was trivial for them.
Before this change there was lots of duplicated code in all the
dircache using backends to support DirMove.
This change factors this code into the dircache library.
Dircache was changed to:
- Remove special cases for the root directory
- Remove Fatal errors
- Call FindRoot on behalf of the user wherever possible
- Bring up to modern Go standards
Backends were changed to:
- Remove calls to FindRoot
- Change calls to FindRootAndPath to FindPath
- Don't make special cases for the root
This fixes several corner cases, for example removing a non existent
directory if FindRoot hasn't been called.
